As is known, a gas turbine for aeronautic engines generally comprises one or more rotating bladed rotors, each of which, in turn, comprises a turbine disk and a crown of blades that surround the turbine disk, with each one having its root retained in a peripheral seat or slot of the turbine disk.
The turbine disks are components that, as well as being subjected to high mechanical stress due to the high speeds of rotation, are subjected to high thermal stress, as they operate in an extremely high temperature environment due to close vicinity with the flow of hot gases that impact the blades.
For optimal turbine operation it therefore becomes necessary to control the operating temperature of these turbine disks, maintaining the operating temperature below a predefined or critical threshold value.
To that end, it is known to bleed a certain air mass air from the compressor associated with the turbine and to feed this air mass to the area of connection of the blades to the turbine disk. In the area of connection of the blades to the disk, the air is forced to flow through axial passages having lengths equal to the thickness of the disk, each one being defined by the bottom of the associated slot on one side, and by the root of the corresponding blade, on the other. In the course of passing through the passages, the air carries away part of the heat from the disk.
Although utilized, the described cooling method is found to be less than satisfactory and, in any case, unable to permit uniform cooling of the turbine disk. That which has just been described results from the fact that during its advance through the passages, the temperature of the air progressively rises and, in consequence, the turbine disk has variable point-to-point temperatures. In addition to this, in known solutions, the dimensions of the airflow duct and its height in particular are practically unchangeable, as they are set by the geometric characteristics and by the dimensions of the root-disk coupling.
The root-disk coupling also determines the geometry of the section of the air passage that, as is known, has a maximum radial size at the centre, i.e. along an axis of symmetry of the root, and drops to zero at the lateral root-disk contact points. This produces a concentration of air in the central area and minimum flow in the lateral areas, where cooling of the disk is consequently found to be less effective with respect to the central area.